Measuring device



3m. 33, l942- G. H. RocKwooD. JR 2,259,603

MEASURING DEVICE Filed Sept. '7, 1959 AT TURA/EV Patented iian. i139 w42l gaat oFrcE t, N. J., assigner to )Bell Telephone itabotories,incorporated,

New York, N. Y., a corporation or New York Application September 7,i939, Serial No. 293,777

(Ci. l--l83) These and other objects of the invention are realized bymeans of a measuring system in which two condensers, which are normallyconnected to a common source oi voltage, are maintained in a chargedcondition .by said source until the beginning ofthe interval to bemeasured; in which both condensers are automatically disconnected fromthe charging source at the commencement of the interval, one oi saidcondensers being isolated to retain its charge and the other beingpermitted to dissipate its charge at a constant rate through aspace-discharge tube until the end specication, disclosesa measuringsystem embodying the features of this invention.

In this system the condensers l and 2 receive charges from. the voltagesourced and utilize these charges to measure an interval of time. Thecharging circuit over which current ows from the source 3 to thecondensers i and 2includes the Adischarge tubes 'fi and 5, which may beeither of the gas-filled or vacuum tupes. Normally the voltage of thesource Si is sumcient to cause the tubes d and 5 to conduct, permittingcurrent to now from the source i through the tubes to the condensers iand 2. Both condensers are charged, therefore, to a voltage which issubstantially the same as the voltage of the source 3.

When itfis desired to measure an interval of time, such as the operatingtime of a relay, the charging circuit for the condensers 'Il and 2 isopened to maris the commencement of the inter-l val. To obtain thisopening of the charging circuit precisely at the instant the measuredinterof said interval; in which the space-discharge tube is renderednon-conducting at the termination of the interval to stop the dischargefrom said second condenser; and in which the charge remaining on saidsecond condenser is compared with that on the :drst condenser byconnecting .both condensers through an indicating instrument todetermine the time elapsed between the beginning and the end of saidinterval.

Morespeciiically, this measuring system may be used to determine theoperating time of a relay. v.at the instant energizing current isapplied to the winding of the relay an impulse is produced whichoperates a gas-iilled tube and causes the disconnection of the twocondensers from the source of charging voltage. The iirst condenser,onbeing disconnected from the charging source, is completely isolatedand retains its charge. The second condenser, however, being connectedacross the discharge path of a pentode'tube, dissipates its chargethrough the tube at a constant rate. As soon as the relay operates,marking the termination of the interval being measured, an impulse isproduced which operates av Asecond gas-lled tube to render the pentodetube non-conducting, thus preventing any further dissipation of thecharge on the second condenser. The operation of the second gas-nlledtube also results in the energization of a relay which connects the twocondensers in series with eachl other'through a galvanometer. Thedilerence in potential between the two condensers is directlyproportional to the time required for operating val begins agas-lled-discharge tube 6 is connected-across the charging circuit. Ifan impulse is delivered over the start circuit l at the instant themeasured interval begins, the tube e fires and closes a low-impedancecircuit across the charging circuit, shunting the tubes i and 5 and thecondensers i and 2. This shunt causes the tubes i and 5 to becomenon-conducting instantly, terminating any further charging of thecondensers.

The condenser i is isolated as soon as the tubes d and 5 cease toconduct; consequently this condenser retains the charge it has receivedfrom the source .3. rIhe condenser Z, however, is connected through aresistance 8 across the anode and cathode terminals of the pentodedischarge Atube 9. rlhe control grid Il)v of the pentode tube isnormally biased by the. battery il with respect to the cathode i2 suchthat current is permitted vto iow in the anode-cathode circuit of thetube. As

soon, therefore, as the charging circuit of condenser 2 is disabled, thecondenser 2 commences -tion of the charge on the condenser 2 continues'In order to mark the termination of the measured interval a. secondgas-lled tube i6 is provided. If, at the end of the interval, an impulseis applied tothe stop circuit l1, the tube I6 res and modies the bias ofthe pentode 9 to such an" extent that the latter tube ceases to conduct,

, conductive in response and the discharge of condenser 2 is terminated.The operation of the tube I6 also brings about the energization of arelay I8 which serves to connect the condensers I and 2 in series withvarying from fractions of a second to several# seconds. However, theinvention is not limited to any particular range of intervals; and itwill be obvious that the length ofthe intervals may Since the condenser2 has dis-l negative pole of battery 3. This shunt across the chargingcircuit causes the tubes 4 and 5 to quench instantly, terminating theflow of charging current to condensers I and 2. The tube 6 being of thegas-lled type, continues to conduct, independently of the start circuit1, to maintain the shunt across -the'charging circuit.

The quenching of the tubes 4 and 5 isolates the condenser I, and thiscondenser retains throughout the measuring interval the charge itderived from the source 3. The condenser 2, however, commences todissipate its chargethe instant the tubes 4 and 5 quench, which is the.same instant that energizing current begins to be extended by selectingthe proper values for the elements used in the system.

' One useful application for this system is the measurement of relayoperating times. For example, the time required for the relay 20 toclose its contacts after the closure of its energizing circuit may beobtained with a high degree of accuracy. The energizing circuitof therelay 20 'is connected in parallel with. the start circuit 1 so that astarting impulse is transmitted to the tube 6 the instant the relay 20begins to energize. Also the contacts of the relay 20 are connected inseries with the stopcircuit I1 to transmit an impulse to the tube IB theinstant relay 20 closes these contacts.

A detailed description will now be given of the measuring system,assuming that it is desired to determine the operating time of the relay2|). As explained above the ondensers I and 2 are normally maintained ina charged condition by the source 3. vThe terminals of condenser 2 areconnected across the anode and` cathode terminals of the discharge tube9 through the resistance 8, and the bias of the control grid I0,supplied by battery II, is such that the tube is plied thereto as aresult of the charge on the condenser 2 during the measuring` operation.

The impedance of the tube, however, prevents it from shunting thecondenser 2 unduly, and the charge on the condenser is maintained by theow of charging current of the source 3 through the discharge tube 4. l

To initiate the measuring operation the key 2i is operated to close anobvious circuit for energizing'the relay 20; At the same instant a,circuit is closed from the positive pole of the battery 23 in theenergizing circuit of relay 20 over one side of the start circuit 1through the condenser 24 to the control grid of the gas-filled tube 6.The other pole of the battery 23 is connected over the other side of thestart circuit 'l to the cathode of tube 6. The control electrode of thetube 6 is normally biased by a circuit from the negative pole of batteryI I through the resistance 25 to prevent operation of the tube. When,however, the battery 23 is' connected to the control electrode of thetube 6 as above noted, the tubev ionizes and closes a relatively lowimpedance shunt across the conductors 26 and Z1 o. the condensercharging circuit. This shunt may be traced from the positive pole ofbattery 3, conductor 2t, resistance 28, key contacts 29,anode andcathode of the tube (i, conductor 21 to the to the anode voltage ap- A.across the anode iiow in the winding of the relay 29. The circuitthrough which the condenser 2 dissipates its charge may be traced fromthe upper terminal of the condenser to the anode 30 of the tube 9,thence to the cathode I2 and resistance 8 to the other terminal of thecondenser. As discharge current ows from the condenser 2 through theanode circuit of the tube, the voltage impressed and cathode of the tubegradually decreases. It is, however, a well-known characteristic ofthese tubes that the current flowing in the anode circuit issubstantially independent of variations in the anode voltage.

l Therefore, the charge on condenser 2 is dissivance 8 to the cathode oftube I6.

pated at a constant rate throughout the measured interval.

When the relay 20' closes its front contacts to terminate the intervalbeing measured, a circuit. is closed from the positive pole of battery3l, contacts of relay 20 over one conductor of the stop circuit I1through the condenser 32 to the control electrode of the gas-filled tubeI6. The other pole of battery 3| is connected over the other side of thestop circuit I1 through resist- Battery 3| delivers an impulse to thecontrol electrode ci the tube I6, which is normally biased by thenegative pole of battery II through resistance 33, causing the tube toionize. When tube' I6 ionizes a circuit is .closed for theL ow ofcurrent from the positive pole of battery 3 through thekey contacts 34,winding of relay I8, anode and cathode of tube I6 through the resistance8 thence over conductor 21 to the negative pole of battery 3. Currentflowing through the resistance 8 produces a.voltage.drop which acts tobias the control electrode I0 of the tube 9 sufliciently to render thetube non-conducting. Thus the dissipation of the charge on condenser 2ceases, marking the end of the measured interval.

-The relay I8 also operates in the discharge circuit of tube I6 andcloses a circuit for connectingthe two condensers I and 2 in series witheach other and in series with the indicating galvanorneter I9. Thiscircuit may be traced from the upper terminal of condenser 2 to thecontacts of relay I8, galvanometer I9 through the condenser l to thelower terminal of condenser 2. Since condenser I possesses its fulloriginal charge and since condenser 2 has dissipated its charge at aconstant ratel during the interval undergoing measurement, thedifference between the charge on condenser I and the residue on

